There are many potential applications that utilize the location of a User Equipment device (UE) in a cellular communications network. For instance, UE location determination is required for Emergency 911 (E911) services. Further, the UE location performance capabilities are mandated by the Federal Communications Commission (FCC). Also, there are many commercial and user applications that rely on knowledge of UE location. In addition to E911, commercial, and user applications, UE location can be utilized by a cellular communications network to improve spectral efficiency. In particular, spectral efficiency scheduling at a base station (e.g., an enhanced Node B (eNB)) allows for use of the same time and frequency radio resources for multiple UEs that are, due to their locations, isolated from a Radio Frequency (RF) perspective. For example, two UEs on different floors of the same building may be assigned the same time and frequency radio resources without concern for co-interference.
There are many existing technologies that can be employed to determine UE location. One well-known and often used technology is the Global Positioning System (GPS). Further, some cellular communications networks (e.g., 3rd Generation Partnership Program (3GPP) Long Term Evolution (LTE) and other Radio Access Technologies (RATs)) use a cell Identifier (ID), UE range either determined from uplink or downlink signals, etc. to determine the location of a UE. However, in many instances, these technologies suffer difficulties in indoor and shared cell environments and become less effective or ineffective for UE location purposes. In particular, a UE equipped with a GPS receiver will not have access to the GPS technology if the GPS receiver is turned off or the GPS receiver is not able to detect a sufficient number of GPS signals (e.g., as when located inside a building). Further, in a small cell, ranging becomes less effective if the range accuracy is on the order of the cell size of the small cell.
Thus, there is a need for systems and methods for determining the location of a UE that is particularly well-suited for small-cell, indoor environments.